IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
LYMPHOID TISSUE NEOFORMATION AFTER VACCINATION WITH DENDRITIC CELLS LOADED WITH APOPTOTIC/NECROTIC B16 MELANOMA CELLS
Autor/es:
SOLEDAD MAC KEON; SILVINA GAZZANIGA; JULIETA MALLERMAN; ALICIA INÉS BRAVO; JOSÉ MORDOH; ROSA WAINSTOK
Lugar:
Lugano
Reunión:
Congreso; the 11th International Symposium on Dendritic Cells in Fundamental and Clinical Immunology DC2010: Forum on Vaccine Science; 2010
Institución organizadora:
the Institute for Research in Biomedicine (IRB) & the Swiss Vaccine Research Institute
Resumen:
Antigen presentation by dendritic cells (DC) is of key importance for the initiation of the primary immune response. Melanoma is an immunogenic cancer and many strategies have employed DC to enhance specific immunity in preclinical models and in clinical studies. Our vaccination scheme, which consists of 4 s.c. injections of 200,000 DC charged with B16-F1 apoptotic/necrotic (Apo/Nec) melanoma cells (DC-Apo/Nec), generates 80% protection against tumor challenge. Since only about ~0,5 % injected DC in the footpad migrated to draining lymph nodes, the aim of this study was to assess vaccine cell migration in our system and investigate if there is an immunological response taking place at the vaccination site. 200,000 DC-Apo/Nec or vehicle (PBS) were injected s.c. once a week, for 4 weeks. The B16 challenge (13,000 viable cells) was administered on the contralateral flank to the last vaccine. To assess DC-Apo/Nec biodistribution, the cells were stained with DiR before being administered. We observed that the cells composing the vaccine accumulated at the vaccination site up to 5 days postvaccination. By flow cytometry analysis we assessed that 0.8 % of DC migrated to draining lymph nodes. To characterize how DC-Apo/Nec interacted locally with the host immune system to elicit resistance to tumor growth, the site of injection was analyzed by hematoxylin-eosin, immunofluorescence and confocal microscopy analysis. The formation of a pseudocapsule, peripheral node addresin (PNAd) expression in small venules, and the recruitment of a wide variety of cellular populations, including macrophages, polymorphonuclear leukocytes, and CD8+ and CD4+ T lymphocytes (16 and 52 fold higher than the controls, respectively) found in association with DC, evidenced the formation of tertiary lymphoid tissue at the vaccination site. With DC, Apo/Nec, DC+Apo/Nec, or PBS administration it was not possible to find this structure. This neo-formation depended on a 24 hour coculture between DC and melanoma cells. In addition, we found lymphotoxin-β mRNA in the disaggregated cells of the vaccination site corroborating the formation of a lymph node-like structure. To discard the possibility that the B16 viable cells were rejected by a local inflammation due to the previous administration of the DC-Apo/Nec cells in the same site, mice were vaccinated on one flank and challenged on the contralateral flank. 90% of the animals remained tumor- free 10 weeks after being challenged, compared to 10 % in the control group (PBS) (Logrank Test p <0.01). Therefore, the lack of tumor growth previously reported is in fact due to systemic protection and not to a local effect produced by the vaccine. We propose that repeated DC-Apo/Nec injection, which have previously phagocytosed and processed ex vivo tumor antigens, establish a state of chronic inflammation. High endothelial venules decorated with PNAd are generated, and naïve lymphocytes arrive, establishing a tertiary lymphoid tissue. These lymphocytes are educated by DCApo/ Nec cells and start the systemic protection. Poor DC migration to the regional lymph nodes leaves an accumulation of antigen-loaded DC at the injection site which could prime locally CD4+ and CD8+ T lymphocytes and contribute to establish a potent anti-tumoral immune response. In our experimental system, a proper antigenic processing and DC maturation is necessary to trigger the formation of tertiary lymphoid tissue.